Liner anchor



March 1968 F. P. GRIBBIN LINER ANCHOR Filed Dec. 23, 1965 United States Patent Ofifice 3,374,835 Patented Mar. 26, 1968 3,374,836 LINER ANCHOR Franklin P. Gribbin, P.O. Box 2102, Bakersfield, Calif., 93303 Filed Dec. 23, 1965, Ser. No. 516,048 6 Claims. (Cl. 16651) ABSTRACT OF THE DISCLOSURE Anchor elements for a perforated liner in an oil well are located at the lower end of the liner, leaving the upper end unrestrained. This eliminates creep resulting from repeated thermal expansion and contraction cycles.

The present invention is concerned generally with oil well equipment, and more particularly with a perforated liner, oftentimes referred to as a slotted pipe, with an anchor for holding the liner in place opposite the producing formation.

There are various types of perforated liners used in producing wells, the liner normally being located in the well opposite the production zone and forming a portion of means for filtering out sand or other foreign material from the oil and gas produced by the well. One type of perforated liner is that suspended at its upper end from the next larger diameter of tubing or casing, by means of expansible slip jaws. In this arrangement, the perforated liner is attached to a hanger which is placed by a suitable type of retrievable tool. The slip jaws on the hanger are expanded to engage the casing from which the perforated liner is suspended, rather than resting the liner on the bottom of the bore hole. In order to obtain the filtering action, space around the liner is filled with gravel or the like through which the oil passes to reach the perforations in the liner. Oil entering the liner then ascends through the liner and the casing or tubing on the upper end of the liner.

Problems have arisen with perforated liners suspended in this manner when some of the various secondary recovery techniques have been used that employ superheated water or steam. During the portion of the cycle in which the formation is treated with the superheated Water or steam, the liner is heated to the temperature of the treatment fluids employed and as a consequence expands. This thermal expansion of the liner causes it to elongate. Since the lower end of the liner is normally held quite firmly against movement downwardly, the result is that the upper end of the liner rises, since the slip jaws do not oppose this motion.

However, during the second half of the recovery cycle, when oil is being produced from the well, the liner cools and correspondingly undergoes thermal contraction. Since the slip jaws resist downward movement of the upper end of the liner, the result is that the upper end stays at the elevated position and the contraction of the liner lifts the lower end.

Repetition of this cycle of heating and cooling has been found in many cases to cause the perforated liner to creep upwardly in the casing, sometimes as much as 50-75 feet. The result is that the liner is no longer properly located with respect to the production zone and a substantial loss of production may result therefrom. The only way to correct this situation is to remove the liner, clean out the well, and re-install the liner. Sometimes this remedial action is impossible because the liner cannot be withdrawn; but even when this can be done, the operation is a very costly one, both in terms of the labor required and in the loss of production from the well during the rehabilitation period.

Thus it becomes a general object of the present invention to provide a suitable means for anchoring a perforated liner in a well at a desired position so that repetition of the thermal cycle of heating and cooling does not cause the liner to change its position.

More specifically, it is an object of the present invention to provide means for anchoring the liner at its lower end to prevent the liner from creeping upwardly, while still leaving the liner free at the upper end to contract and expand as required during the application of secondary recovery techniques.

These objects of'the present invention are achieved by providing, in combination with a perforated liner adapted to be lowered into a bore hole through casing set in the hole, expandable anchor means near the lower end of the liner which includes means engaging the wall of the bore hole to resist upward travel of the liner. The expandable anchor means includes a plurality of pivoted arms held initially in retracted position but swingable outwardly into engagement with the wall of the bore hole to resist upward movement of the liner. The arms are held retracted by frangible means, preferably broken by contact with the bottom of the hole. Other breakable means may be provided to permit the arms to be collapsed for withdrawal of the liner upwardly through the casing. The liner preferably extends upwardly into the casing but is not suspended therefrom, an adapter being used to reduce clearance between the liner and the casing sufliciently to eliminate substantially any opening between the liner and the casing at the upper end of the liner, while still allowing relative sliding movement between the liner and easing.

How the above objects and advantages of the present invention, as well as others not specifically referred to herein, are achieved will be better understood by reference to the following description and to the annexed drawing, in which:

FIG. 1 is a fragmentary longitudinal vertical section through a bore hole and the lower end of easing therein, showing a perforated liner and .anchor means therefor in normal operative position in the bore hole.

FIG. 2 is a fragmentary vertical section similar to FIG. 1, showing the anchor means at the bottom of the liner in section with the parts in the positions occupied as the .anchor is lowered through the casing.

FIG. 3 is a view similar to FIG. 2 showing the anchor arms released and in partly extended position to engage the formation.

FIG. 4 is a traverse horizontal section on FIG. 2.

FIG. 5 is a fragmentary side elevation at a reduced scale on line 55 of FIG. 2.

Referring now to the drawing, and more particularly to FIG. 1, there is indicated at 10 a bore hole extending downwardly into the ground from the surface of the earth to an oil-producing formation at 11. Inside the bore is casing 12 which generally terminates at some position above the producing zone 11. Between casing 12 and the wall of bore hole 10 there may be a body of cement 14 placed in order to isolate the production zone from the well bore above.

The perforated pipe or liner is indicated generally at 16. It is an elongated, tubular member generally made by slotting or otherwise perforating a piece of pipe having a diameter smaller than the internal diameter of casing 12 so that the liner can be lowered easily inside the casing to a position opposite production zone 11. Liner 16 has a plurality of openings 17 which may be of any desired size and shape, the nature of the openings and the method of making them being of no consequence as far as the present invention is concerned.

Attached to the lower end of liner 16 is the anchor means indicated generally at 20. This anchor may be attached to the liner in any suitable manner, as, for

line 44 of 3 example, by welding the body of the anchor to the liner or by thread .and coupling.

Anchor 20 comprises body 21 on which is pivotally mounted a pair of anchor arms 22. Each arm 22 is pivotally mounted on body 21 by pivot pin or shaft 23, each arm preferably being rotatable with respect to pin 23 for reasons which will become apparent. Pins 23 are typically welded in place.

The anchor as shown here has but a single pair of arms 22. However, it will be realized that additional arms, preferably in pairs but in any suitable arrangement, may be provided, as desired.

Body 21 has a central web 25 on opposite sides of which are mounted a pair of leaf spring blades 26. The lower free end of each blade bears against an adjacent arm 22, urging the arm to rotate in a direction to swing the free end of the arm outwardly against the formation. In addition, the arms are pivoted at their lower ends and so they are gravity biased to swing outwardly from the position of FIG. 2 to the position of FIG. 3.

In order to restrain arms 22 as the anchor is lowered downwardly through casing 12, the upper free ends of the two anchor arms are connected by a frangible member, such as wire 28, which passes through central web 25.

Web 25 has a central bore 29 in which is slidably mounted plunger 30. Plunger 39 carries on its lower end disc 31 to provide an enlarged head. A U-shaped stirrup 33 fastened to the lower end of body 21 is engaged by head 31, as shown in FIG. 2, to keep plunger 30 from falling out of bore 29.

When the liner and its anchor are lowered into the bore hole, they are lowered until they strike the bottom of the hole. This may be actually the extreme end of the hole drilled by the bit; but is likely to be something short of this since there is generally some accumulation of cuttings and debris in the bottom of the hole. Such accumulation is indicated at 34 in FIG. 3. Stirrup 33 penetrates into this accumulation of debris and thus brings disc 31 into engagement with it. The resistance to downward travel of the plunger because of the enlarged surface presented by the head 31 causes plunger 30 to rise in bore 29. The web holds the wire against upward movement by the plunger; and the plunger engaging the wire where it extends out beyond the vertical face of bore 29 shears wire 28, as indicated in FIG. 3. The combined action of gravity and the force of springs 26 acting on arms 22 causes them to pivot in opposite directions to move their upper free ends outwardly of the tool and into contact with the wall of the bore hole, as shown in FIG. 3.

In this position, arms 22 dig into the earth formation. Substantial penetration of the formation can be effected now by lifting upwardly on the liner which is still connected to a retrievable setting tool 35 on a string of pipe extending upwardly to the surface. By moving the liner upwardly a short distance, the anchor arms can be forced into the side wall of the hole until they assume a position somewhat as shown in FIG. 1. This movement is effected under close control of the force applied upwardly to the liner as measured by the weight indicator on the rig at the top of the hole.

In order to fill in the annular space between the perforated liner and the inside of casing 12, an annular adapter 36 is preferably attached to the liner at its upper end. This adapter is of such radial dimension as to substantially fill the space between the liner and the casing and thereby center the liner in the casing. The clearance between the adapter and the casing may be adjusted to any desired value, preferably being kept to a minimum and typically being only a few hundredths of an inch. This arrangement permits sliding movement between the casing and liner as the latter expands upon being heated and contracts when subsequently cooled; but there is no firm connection between the casing and liner which causes the liner to be held by the casing against free movement in either direction relative thereto.

In the event that it is anticipated the liner may be removed from the well, means are provided for causing arms 22 to collapse. For this purpose, each pivot pin 23- is provided with a shear pin 38 which projects beyond the pivot pin and into a slot 22a in the end of the arm, such slot having an angular length of at least and preferably somewhat more. If, after re-connecting tool 35 to the liner, a sufiicient upward pull is exerted on the liner by equipment at the well head, not shown, the two pins 38 can be sheared and the two arms 22 collapsed to the broken line position 22b shown in FIG. 1. In this position, the arms do not project outwardly beyond body 20 for any substantial distance and the liner and its anchor can be withdrawn upwardly through the interior of casing 12. Pins 38 can be designed to shear at some sufficiently high predetermined value, for example, 50,000 pounds, which ensures that the anchor will not allow the liner to move upwardly in the well as a result of thermal expansion and contraction but which is within the capacity of the tools and the draw works at the well head, thereby allowing the liner to be pulled out of the well should occasion arise.

The anchor means of the present invention may be used with any of the types of liners now in common use. At times a liner is used in an open hole; but it may be surrounded with gravel as shown to hold back sand. For this purpose, the gravel may be held in a sheath around the liner, referred to as a pre-packed liner, or the gravel may be flow packed after the liner is in place producing a gravel layer of the nature illustrated; but the invention is not limited to any of these specific arrangements.

From the foregoing description, it will be apparent that various changes in the detailed construction of the liner and the anchor attached thereto may be made by persons skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the foregoing description is considered as being illustrative of, rather than limitativeupon, the invention defined by the appended claims.

I claim:

1. The combination comprising:

a perforated liner adapted to be lowered into a bore hole through casing set in the hole;

and expandable anchor means near the lower end of the liner including means engageable with the wall of the bore hole to resist upward travel of the liner in the bore hole,

said anchor means including a plurality of pivoted arms swingable outwardly into engagement with the wall of the bore hole to resist upward travel of the liner.

2. The combination as in claim 1 in which the anchor means includes frangible means holding the arms initially in retracted position.

3. The combination as in claim 1 in which the anchor means includes frangible means holding the arms initially in retracted position and means operated by contact with the bottom of the bore hole to break said frangible means.

4. The combination as in claim 1 which includes limiting means restraining the-arms against movement beyond an operative position, said limiting means being shearable by upward movement of the liner to collapse the arms for withdrawal through the casing.

5. The combination comprising:

a length of casing set in a bore hole in the ground;

a perforated liner extending below the casing into the bore hole and slidably engaging the inside of the casing at the upper end of the liner;

and anchor means attached to the liner near the lower end thereof and including extensible members engageable with the wall of the bore hole to anchor the liner at its lower end against upward movement,

said anchor means including:

, 6 a plurality of pivotally mounted arms gravityfrangible means holding the arms out of engagementbiased into engagement with the bore hole wall; with the bore hole wall; frangible holding means holding said arms in reand limiting means restraining the arms against movend i i ment beyond an operative position, said limiting and means operable by contact with the formation 5 means being Shearable by upward movement of th@ anchor to collapse the arms for withdrawal from below the casing to break said holding means the bore hole.

and release the arms for swinging movement toward the side wall of the bore hole.

f C' 6. An anchor for anchoring a member in a bore hole Re erences in the ground, comprising: 10 UNITED STATES PATENTS a body attached to said member; 12/1903 Karsch 6 a plurality of arms pivotally mounted on the body and g; a f f swingable outwardly into engagement with the wall 2585369 2/1952 C 1 lams 21 aruthers 175276 of the bore hole to reset upward travel of the at- 15 2 965031 12/1960, Johns 16,6 214 tached member; means biasing the arms toward said engagement; JAMES A. LEPPINK, Primary Examiner. 

